JP2008019730A - Exhaust gas recirculating device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for reducing exhaust emission, and restraining misfire of an internal combustion engine, by making the EGR ratio follow a target value, by properly changing the fresh air volume, even when the mixing ratio of a low pressure EGR gas quantity with a high pressure EGR gas quantity is changed, in an exhaust gas recirculating device of the internal combustion engine. <P>SOLUTION: This exhaust gas recirculating device has a turbocharger having a turbine arranged in an exhaust gas passage and a compressor arranged in an intake passage, a low pressure EGR passage, a high pressure EGR passage, and a target fresh air volume correcting means (S103) correcting the target fresh air volume by a factor interlocked with a change in the mixing ratio of the low pressure EGR gas quantity and the high pressure EGR gas quantity, when the mixing ratio of the low pressure EGR gas quantity and the high pressure EGR gas quantity is changed in the middle of making the fresh air volume follow the target fresh air volume. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

A low-pressure EGR passage that takes in a part of exhaust gas from an exhaust passage downstream of the turbine as low-pressure exhaust gas recirculation (hereinafter referred to as EGR) gas and recirculates the low-pressure EGR gas to an intake passage upstream of the compressor, and an exhaust gas upstream of the turbine A high-pressure EGR passage that takes in part of the exhaust as high-pressure EGR gas from the passage and recirculates the high-pressure EGR gas to the intake passage downstream of the compressor, and effectively uses these passages for power performance and EGR control. A technique for reducing exhaust emission in a wide operation range without impairing controllability and responsiveness is known (see, for example, Patent Document 1).
JP 2004-150319 A

  By the way, in the apparatus using both the low pressure EGR passage and the high pressure EGR passage as in the technique of Patent Document 1, the EGR rate corresponding to the ratio of EGR gas contained in the intake air sucked into the internal combustion engine is uniformly equal. Even in this case, the amount of fresh air drawn into the internal combustion engine from the outside changes depending on the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount.

  For this reason, when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed, unless the new air amount is changed appropriately, the EGR rate does not follow the target value, and the exhausted nitrogen oxide ( NOx) and hydrocarbon (HC) increase may cause exhaust emission deterioration and internal combustion engine misfire.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a new recirculation device for an internal combustion engine even when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed. An object of the present invention is to provide a technique for appropriately changing the air volume, causing the EGR rate to follow a target value, reducing exhaust emission, and suppressing misfire of the internal combustion engine.

In the present invention, the following configuration is adopted. That is,
A turbocharger having a turbine disposed in an exhaust passage of the internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes a part of the exhaust gas as a low pressure EGR gas from the exhaust passage downstream of the turbine and recirculates the low pressure EGR gas to an intake passage upstream of the compressor;
A high-pressure EGR passage that takes a part of exhaust gas as a high-pressure EGR gas from an exhaust passage upstream of the turbine and recirculates the high-pressure EGR gas to an intake passage downstream of the compressor;
When the mixing ratio of the low-pressure EGR gas quantity and the high-pressure EGR gas quantity changes while the new air quantity is made to follow the target fresh air quantity, the mixing ratio of the low-pressure EGR gas quantity and the high-pressure EGR gas quantity changes. Target fresh air amount correcting means for correcting the target fresh air amount by a linked coefficient;
An exhaust gas recirculation device for an internal combustion engine.

  Here, when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed, the EGR rate will not follow the target value unless the fresh air amount is appropriately changed, and the exhausted NOx and HC In some cases, the exhaust emission may be worsened and the internal combustion engine may be misfired.

  Therefore, in the present invention, when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount changes while the fresh air amount is made to follow the target fresh air amount, the low pressure EGR gas amount and the high pressure EGR gas amount. The target fresh air amount is corrected by a coefficient linked to the change in the mixing ratio.

  According to this, the target fresh air amount is corrected to an appropriate value by a coefficient linked to the change in the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount, and the new air amount follows the target fresh air amount. The amount can be changed appropriately. Therefore, even when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed, the fresh air amount can be appropriately changed, and the EGR rate can be made to follow the target value. Therefore, it is possible to suppress the increase in exhausted NOx and HC, reduce the exhaust emission, and suppress the misfire of the internal combustion engine.

  The coefficient is calculated from a function using the opening degree of the low pressure EGR valve for adjusting the low pressure EGR gas amount in the low pressure EGR passage and the opening degree of the high pressure EGR valve for adjusting the high pressure EGR gas amount in the high pressure EGR passage as variables. Good. The coefficient may be calculated from a function using an actual boost pressure downstream of the compressor and a predetermined base boost pressure as variables. Furthermore, the coefficient may be calculated from a function using the actual rotational speed of the turbine and a predetermined base rotational speed as variables.

  According to these, the coefficient is linked to the change in the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount, and the target fresh air amount can be corrected to an appropriate value.

  The predetermined base supercharging pressure is, for example, a mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount, such as a supercharging pressure when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is 1: 1. Is the basic supercharging pressure determined in advance. Further, the predetermined base rotational speed is, for example, the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount, such as the rotational speed of the turbine when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is 1: 1. Is the basic rotation speed of the turbine determined in advance.

  According to the present invention, in the exhaust gas recirculation apparatus for an internal combustion engine, even when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed, the fresh air amount can be appropriately changed, and the EGR rate is made to follow the target value. Exhaust emissions can be reduced and misfire of the internal combustion engine can be suppressed.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas recirculation apparatus for an internal combustion engine according to this embodiment is applied and its intake / exhaust system.

  An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.

An intake passage 3 is connected to the internal combustion engine 1. In the middle of the intake passage 3, a compressor housing 5a of a turbocharger 5 that operates using exhaust energy as a drive source is disposed. A first throttle 6 for adjusting the flow rate of intake air flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the compressor housing 5a. The first throttle 6 is opened and closed by an electric actuator. An air flow meter 7 that outputs a signal corresponding to the flow rate of fresh intake air (hereinafter referred to as fresh air) flowing through the intake passage 3 is disposed in the intake passage 3 upstream of the first throttle 6. . With this air flow meter 7,
The fresh air amount of the internal combustion engine 1 is measured.

  An intercooler 8 that performs heat exchange between the intake air and the outside air is disposed in the intake passage 3 downstream of the compressor housing 5a. A second throttle 9 for adjusting the flow rate of the intake air flowing through the intake passage 3 is disposed in the intake passage 3 downstream of the intercooler 8. The second throttle 9 is opened and closed by an electric actuator.

  On the other hand, an exhaust passage 4 is connected to the internal combustion engine 1. In the middle of the exhaust passage 4, a turbine housing 5b of the turbocharger 5 is disposed. A particulate filter (hereinafter simply referred to as a filter) 10 is disposed in the exhaust passage 4 downstream of the turbine housing 5b. The filter 10 carries an NOx storage reduction catalyst (hereinafter simply referred to as NOx catalyst). The filter 10 collects particulate matter in the exhaust gas. Further, the NOx catalyst occludes NOx in the exhaust when the oxygen concentration of the exhaust flowing into the NOx catalyst is high, while the NOx that occluded when the oxygen concentration of the exhaust flowing into the NOx catalyst decreases. Release. At that time, if reducing components such as HC and carbon monoxide (CO) are present in the exhaust, NOx released from the NOx catalyst is reduced. Note that an oxidation catalyst or a three-way catalyst may be supported on the filter 10 instead of the NOx catalyst.

  An exhaust throttle valve 11 that adjusts the flow rate of the exhaust gas flowing through the exhaust passage 4 is provided in the exhaust passage 4 downstream of the filter 10. The exhaust throttle valve 11 is opened and closed by an electric actuator.

  The internal combustion engine 1 is provided with a low pressure EGR device 30 that recirculates (recirculates) part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a low pressure. The low pressure EGR device 30 includes a low pressure EGR passage 31, a low pressure EGR valve 32, and an EGR cooler 33.

  The low pressure EGR passage 31 connects the exhaust passage 4 downstream of the filter 10 and the intake passage 3 upstream of the compressor housing 5 a and downstream of the first throttle 6. Through this low-pressure EGR passage 31, the exhaust gas is recirculated to the internal combustion engine at a low pressure. In this embodiment, the exhaust gas recirculated through the low pressure EGR passage 31 is referred to as low pressure EGR gas.

  Further, the low pressure EGR valve 32 adjusts the amount of the low pressure EGR gas flowing through the low pressure EGR passage 31 by adjusting the passage sectional area of the low pressure EGR passage 31. Further, the EGR cooler 33 exchanges heat between the low-pressure EGR gas passing through the EGR cooler 33 and the cooling water of the internal combustion engine 1 to lower the temperature of the low-pressure EGR gas.

  The internal combustion engine 1 is provided with a high-pressure EGR device 40 that recirculates a part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a high pressure. The high pressure EGR device 40 includes a high pressure EGR passage 41 and a high pressure EGR valve 42.

  The high-pressure EGR passage 41 connects the exhaust passage 4 upstream of the turbine housing 5 b and the intake passage 3 downstream of the second throttle 9. Through this high-pressure EGR passage 41, the exhaust gas is recirculated to the internal combustion engine at a high pressure. In this embodiment, the exhaust gas recirculated through the high pressure EGR passage 41 is referred to as high pressure EGR gas.

  Further, the high pressure EGR valve 42 adjusts the amount of high pressure EGR gas flowing through the high pressure EGR passage 41 by adjusting the passage sectional area of the high pressure EGR passage 41.

  The internal combustion engine 1 configured as described above is provided with an ECU 12 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 12 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  Further, the ECU 12 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 13 by the driver, and an accelerator opening sensor 14 that can detect the engine load and a crank position sensor 15 that detects the engine speed are electrically wired. The output signals of these various sensors are input to the ECU 12.

  On the other hand, the ECU 12 is connected to the first throttle 6, the second throttle 9, the exhaust throttle valve 11, the low pressure EGR valve 32, and the high pressure EGR valve 42 through electrical wiring, and these devices are controlled by the ECU 12. Is done.

  Then, a new fresh air amount measured using the air flow meter 7 is controlled by controlling these devices such as the first throttle 6, the second throttle 9, the exhaust throttle valve 11, the low pressure EGR valve 32, and the high pressure EGR valve 42. The air volume (measured fresh air volume) is made to follow. It should be noted that the target fresh air amount here depends on the operating state and environmental conditions of the internal combustion engine 1 so that the intake EGR rate matches the target value when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount does not change. The value is set as appropriate.

  In this way, while the fresh air amount is made to follow the target fresh air amount, for example, when the temperature of the cooling water circulating around the cylinder 2 of the internal combustion engine 1 is low, the temperature of the cylinder 2 is raised. The ratio of the high-pressure high-pressure EGR gas sucked into the internal combustion engine 1 is increased, or the ratio of the low-temperature low-pressure EGR gas quantity is increased as the coolant temperature rises, so that the low-pressure EGR gas quantity and high-pressure are increased. The mixing ratio of the EGR gas amount may be changed.

  If the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed, unless the new air amount is changed appropriately, the EGR rate of the intake air will not follow the target value, and the amount of EGR gas in the intake air will be excessive. There are cases where the exhaust emission becomes worse, such as an increase in NOx and HC discharged from the internal combustion engine 1 at a small ratio, and the internal combustion engine 1 misfires.

  Therefore, in the present embodiment, when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount changes while the fresh air amount is made to follow the target fresh air amount, the low pressure EGR gas amount and the high pressure EGR gas are changed. The target fresh air amount is corrected by a coefficient linked to the change in the mixing ratio of the amount.

That is,
Target fresh air amount Gtrg = basic target fresh air amount Gbase + coefficient α × corrected fresh air amount Gc (Expression 1)
The target fresh air amount is corrected using the formula of

  Here, the target fresh air amount Gtrg is a corrected target fresh air amount corresponding to a change in the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount, and the basic target fresh air amount Gbase is the low pressure EGR gas. This is the basic target fresh air amount before correction that does not correspond to the case where the mixing ratio of the amount and the high-pressure EGR gas amount changes, and the coefficient α is a change in the mixing ratio of the low-pressure EGR gas amount and the high-pressure EGR gas amount. The corrected fresh air amount Gc is a linked coefficient, and is a predetermined amount of fresh air amount used for correction.

And
Coefficient α = Opening of low pressure EGR valve / Opening of high pressure EGR valve (Equation 2)
The coefficient α is calculated using the following equation.

  The opening degree of the low pressure EGR valve and the opening degree of the high pressure EGR valve are obtained by detecting the opening degree of the low pressure EGR valve 32 and the opening degree of the high pressure EGR valve 42 by an opening sensor (not shown). .

  That is, when the opening degree of the low pressure EGR valve 32 increases and / or the opening degree of the high pressure EGR valve 42 decreases, the coefficient α increases and the target fresh air amount Gtrg increases. This is because when the opening of the low pressure EGR valve 32 is increased and / or the opening of the high pressure EGR valve 42 is decreased, the amount of exhaust gas flowing into the high pressure EGR passage 41 on the upstream side of the turbine housing 5b is reduced. Since the amount of exhaust gas that passes through and flows into the low-pressure EGR passage 31 increases, the rotational speed of the turbine in the turbine housing 5b increases, and accordingly, supercharging in the compressor housing 5a is promoted. Therefore, since the amount of intake air taken from the upstream side of the compressor housing 5a increases, the amount of low-pressure EGR gas increases when the amount of fresh air is not increased, and the EGR rate of intake air increases. For this reason, since it is necessary to increase the amount of fresh air so as not to increase the EGR rate of intake air, the target amount of fresh air increases.

As the function for calculating the coefficient α, various functions using the opening of the low pressure EGR valve and the opening of the high pressure EGR valve as variables other than the function of (Equation 2) can be used.
Factor α = F (opening degree of low pressure EGR valve, opening degree of high pressure EGR valve) (Equation 3)
It can be expressed as. In the present embodiment, (Expression 2) is merely illustrated as an example of a function (Expression 3) for calculating the coefficient α.

  The coefficient α may be derived from the map. For example, a map of the relationship between the three parameters of the opening of the low pressure EGR valve, the opening of the high pressure EGR valve, and the coefficient α is obtained in advance from experiments and stored, and the opening of the low pressure EGR valve 32 and the high pressure EGR valve 42 are stored. It is also possible to derive the coefficient α by applying the degree of opening to the map.

  Next, the flow of fresh air amount correction control according to this embodiment will be described. FIG. 2 is a flowchart showing a flow of fresh air amount correction control according to this embodiment. This routine is repeatedly executed every predetermined time. Further, this routine is executed when the measured fresh air amount measured using the air flow meter 7 is made to follow the target fresh air amount.

  In step S101, the ECU 11 determines whether or not the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount has been changed. Whether or not the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed is determined by detecting the opening degree of the low pressure EGR valve 32 and the opening degree of the high pressure EGR valve 42 with an opening degree sensor (not shown) and opening them. The degree is determined by the fact that the degree is opened and closed more than usual.

  When it is determined in step S101 that the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is not changed, the ECU 11 once ends this routine. If it is determined that the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed, the process proceeds to step S102.

  In step S102, the ECU 11 calculates the coefficient α using (Equation 2). Here, the opening degree of the low pressure EGR valve 32 and the opening degree of the high pressure EGR valve 42 are detected by an opening degree sensor (not shown), and the value of the opening degree is substituted into (Equation 2) as a coefficient α. Is calculated.

  The opening sensor (not shown) is a variable that is mounted on the vehicle, does not need to be newly installed, can be reduced in cost, and is directly connected to the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount, A delay due to other factors does not occur, and a reliable numerical value can be detected for calculating the coefficient α.

  In step S103 subsequent to step S102, the ECU 11 calculates the target fresh air amount Gtrg using the calculated coefficient α and (Equation 1). Here, the target fresh air amount Gtrg is calculated by taking the sum of the basic target fresh air amount Gbase and the value obtained by multiplying the coefficient α by the corrected fresh air amount Gc. Then, the measured fresh air amount is made to follow the target fresh air amount Gtrg as a new target fresh air amount. The ECU 11 that executes this step corresponds to the target fresh air amount correcting means of the present invention.

  According to the above embodiment, the target fresh air amount is corrected to an appropriate value (target fresh air amount Gtrg) by the coefficient α linked to the change in the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount, and the target fresh air is obtained. The actual fresh air amount can be appropriately changed by the measured fresh air amount following the amount (target fresh air amount Gtrg). Therefore, even when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is changed, the actual new air amount can be appropriately changed, and the EGR rate of the intake air can be made to follow the target value. Therefore, increase in NOx and HC discharged from the internal combustion engine 1 can be suppressed, exhaust emission can be reduced, and misfire of the internal combustion engine 1 can be suppressed.

(Other examples)
In the above-described embodiment, the case where the coefficient α is calculated by a function using the opening degree of the low pressure EGR valve 32 and the opening degree of the high pressure EGR valve 42 as variables has been described. However, the variable for calculating the coefficient α linked to the change in the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is not limited to the opening degree of the low pressure EGR valve 32 and the opening degree of the high pressure EGR valve 42.

For example,
Coefficient α = actual boost pressure downstream of the compressor housing / predetermined base boost pressure... (Formula 4) may be used to calculate the coefficient α.

  The actual boost pressure downstream of the compressor housing 5a is detected by the boost pressure sensor 16 shown in FIG. The predetermined base supercharging pressure is, for example, a predetermined basic supercharging pressure when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is 1: 1.

  That is, when the actual supercharging pressure downstream of the compressor housing 5a increases, the coefficient α increases and the target fresh air amount Gtrg increases. The fact that the actual supercharging pressure downstream of the compressor housing 5a is large is that the amount of exhaust gas flowing into the high-pressure EGR passage 41 on the upstream side of the turbine housing 5b is reduced and flows into the low-pressure EGR passage 31 through the turbine housing 5b. This is because the amount of exhaust gas to be increased increases the rotational speed of the turbine in the turbine housing 5b, and accordingly, the supercharging in the compressor housing 5a is promoted. Therefore, since the amount of intake air taken from the upstream side of the compressor housing 5a increases, the amount of low-pressure EGR gas increases when the amount of fresh air is not increased, and the EGR rate of intake air increases. For this reason, since it is necessary to increase the amount of fresh air so as not to increase the EGR rate of the intake air, the target amount of fresh air increases.

As the function for calculating the coefficient α, various functions using the actual supercharging pressure downstream of the compressor housing 5a and a predetermined base supercharging pressure as variables other than the function of (Equation 4) can be used. In terms of
Factor α = F (actual supercharging pressure downstream of the compressor housing, predetermined base supercharging pressure) (Equation 5)
It can be expressed as. In the present embodiment, (Expression 4) is merely illustrated as an example of a function (Expression 5) for calculating the coefficient α.

The coefficient α may be derived from the map. For example, a map of the relationship between the three parameters of the actual supercharging pressure downstream of the compressor housing 5a, the predetermined base supercharging pressure, and the coefficient α is obtained in advance from experiments and stored, and the actual supercharging downstream of the compressor housing 5a is stored. The coefficient α may be derived by applying the supply pressure and a predetermined base supercharging pressure to the map.

on the other hand,
Coefficient α = actual turbine rotational speed / predetermined base rotational speed (Expression 6)
The coefficient α may be calculated using the following formula.

  The actual rotational speed of the turbine is detected by a turbine rotational speed sensor 17 shown in FIG. The predetermined base rotational speed is a predetermined basic rotational speed of the turbine when the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount is 1: 1, for example.

  That is, as the actual rotational speed of the turbine increases, the coefficient α increases and the target fresh air amount Gtrg increases. This is because when the actual rotational speed of the turbine is large, the amount of exhaust flowing into the high-pressure EGR passage 41 on the upstream side of the turbine housing 5b decreases, and the amount of exhaust flowing through the turbine housing 5b into the low-pressure EGR passage 31 is reduced. This is because it indicates that the number of rotations of the turbine in the turbine housing 5b is increasing. In response to this, supercharging in the compressor housing 5a is promoted. Therefore, since the amount of intake air taken from the upstream side of the compressor housing 5a increases, the amount of low-pressure EGR gas increases when the amount of fresh air is not increased, and the EGR rate of intake air increases. For this reason, since it is necessary to increase the amount of fresh air so as not to increase the EGR rate of intake air, the target amount of fresh air increases.

As the function for calculating the coefficient α, various functions having variables of the actual rotational speed of the turbine and a predetermined base rotational speed other than the function of (Equation 6) can be used.
Coefficient α = F (actual turbine rotational speed, predetermined base rotational speed) (Expression 7)
It can be expressed as. In the present embodiment, (Expression 6) is merely illustrated as an example of a function (Expression 7) for calculating the coefficient α.

  The coefficient α may be derived from the map. For example, a map of the relationship between the three parameters of the actual turbine speed, the predetermined base speed, and the coefficient α is obtained in advance by experiments and stored, and the actual turbine speed and the predetermined base speed are stored in the map. It is also possible to derive the coefficient α by applying

  The target fresh air amount is corrected to an appropriate value by the coefficient α linked to the change in the mixing ratio of the low pressure EGR gas amount and the high pressure EGR gas amount calculated by the above embodiment, and the measured fresh air amount is adjusted to the target fresh air amount. The actual fresh air amount may be appropriately changed by following the above.

  The exhaust gas recirculation apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention.

1 is a diagram illustrating an internal combustion engine and an intake / exhaust system thereof according to Embodiment 1. FIG. 3 is a flowchart illustrating a flow of fresh air amount correction control according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 4 Exhaust passage 5 Turbocharger 5a Compressor housing 5b Turbine housing 6 1st throttle 7 Air flow meter 8 Intercooler 9 2nd throttle 10 Filter 11 Exhaust throttle valve 13 Accelerator pedal 14 Accelerator opening sensor 15 Crank Position sensor 16 Supercharging pressure sensor 17 Turbine speed sensor 30 Low pressure EGR device 31 Low pressure EGR passage 32 Low pressure EGR valve 33 EGR cooler 40 High pressure EGR device 41 High pressure EGR passage 42 High pressure EGR valve

Claims (4)

A turbocharger having a turbine disposed in an exhaust passage of the internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine;
A low pressure EGR passage that takes a part of the exhaust gas as a low pressure EGR gas from the exhaust passage downstream of the turbine and recirculates the low pressure EGR gas to an intake passage upstream of the compressor;
A high-pressure EGR passage that takes a part of exhaust gas as a high-pressure EGR gas from an exhaust passage upstream of the turbine and recirculates the high-pressure EGR gas to an intake passage downstream of the compressor;
When the mixing ratio of the low-pressure EGR gas quantity and the high-pressure EGR gas quantity changes while the new air quantity is made to follow the target fresh air quantity, the mixing ratio of the low-pressure EGR gas quantity and the high-pressure EGR gas quantity changes. Target fresh air amount correcting means for correcting the target fresh air amount by a linked coefficient;
An exhaust gas recirculation device for an internal combustion engine, comprising:   The coefficient is calculated from a function using the opening degree of the low pressure EGR valve for adjusting the low pressure EGR gas amount in the low pressure EGR passage and the opening degree of the high pressure EGR valve for adjusting the high pressure EGR gas amount in the high pressure EGR passage as variables. The exhaust gas recirculation device for an internal combustion engine according to claim 1.   2. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1, wherein the coefficient is calculated from a function using an actual boost pressure downstream of the compressor and a predetermined base boost pressure as variables.   2. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1, wherein the coefficient is calculated from a function using an actual rotational speed of the turbine and a predetermined base rotational speed as variables.

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